Electrodeposition of organic materials such as rubber and cellulosic compounds



June 15,1926. 1,589,326

S. E. SHEPPARD ET AL 'ELECTRODEPOSITION OF ORGANIC MATERIALS, SUCH AS RUBBER AND CELLULOSIG COMPOUNDS Filed April 22, 1925' A DIFFUSION PATH FOR THE. CURRENT IS FORMED BY A PRELIMINARY Conn/v6, snY orn HYGROSCOPIC COLLOID,

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ATTORNEY can be wholly or largely Patented June 15, 1926 UNITED STATES 1,589,326 PATENT OFFICE.

SAMUEL E. SHEPPARD AND CARL L. BEAL, OF ROCHESTER, YORK, ASSIGNORS TO EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YORK, A CORPORATTON OF- NEW YORK.

ELECTRODEPOSITION OF ORGANIC MATERIALS SUCH .AS RUBBER AND CELLULOSIC COMPOUNDS. 1

Application filed April 22, 1925. Serial No. 25,160.

This invention relates to the electrodeposition of organic materials such, for instance, as rubber and cellulosic Compounds. One object of the invention is to provide a simple and inexpensive process for producing electrodeposited coatings of great uniformity. Another object of the invention is to provide blanks for use in such process which may be kept indefinitely and yet will be ready at any time for the electrodeposition of a uniform coating of said materials. Other objects will hereinafter appear.

In the accompanying drawing, forming a part hereof, the single figure is a diagrammatic cross section of one form of an apparatus which may be employed in carrying out our process.

In. the electrodeposition of organic materials, such as rubber or cellulosic compounds, like nitrocellulose, acetyl cellulose, and cellulose ether, the coatings sometimes become unequal and show undesirably thin spots or pits which impair them. This undesirable efiect may be due to several causes such as locally generated currents and small local electromotive forces which prevent or lessen the deposit of the material at that oint.

We find that such inequality an defects avoided and a smoothness of textureobtained by first covering the surface on which theelectrodeposition is to take lace, with a substratum which forms a di using ath for the current at 1said surface. The su stratum is prefera the efi'ective potential at all the points over said surface. Where the surfaces covered with substratum are to be kept or transported for some time before use, we have found that it is preferable to have the substratum hygrosco ic. We shall now explain, by way of lllustration, the preferred forms of our invention, but it will be understood that the invention is not restricted to such forms, except as indicated in the appended claims.

Suitable materials for the substratum are, for example, gelatin, glue, a mixture of glue and rubber emulsion, artificial rubber emulsions or natural rubber emulsions such as latex. The surface which is to becoated is covered, preferably quite uniformly, with an organic one and tends to-equalize the substratum by any suitable or preferred method, say by dipping, flowing or spraying with the substrating liquid. It is then partially dried so as to form a coherent uniform surface. An" aqueous solution containing from 3 to 5% of gelatin is very useful, as is likewise the natural latex, as preserved with ammonia.

In working on a commercial scale it is often necessary to allow an article, to be coated, to remain some time after the substratum is applied before the final coating takes place. If the substratum dries to a hard, horny mass, it is often slow and difficult to get it into the proper condition for the plating operation. Where the articles are substratumed in one part of the plant and are then stored and transported to a likely to arise. It will not, however, occur if the substratum coating contains one or more hygroscopic substances, such as glycerin, sugars, ,or even hygroscopic salts llke calcium chloride. Just enough of these substances are added to the coating bath so that when the substratum coating is formed on the surface it will contain enough hygroscopic material to kee it from becoming horn and hard under the prevailing atmospheric conditions. The percentage of hygroscopic substance is readily adjusted in any instance. lVhenthe hygroscopic materials are to be added to the latex, they are preferably made slightly alkaline by a mixture of ammonia or similar material in order to insure against accidental coagulation.

The substratumed electrode surfaces thus produced are adapted to receive uniform electrodeposited coatings by any of the processes for electrodepositing organic material from a ucous emulsions thereof. A typical example of such a process is in U. S. Patent No. 1,476,374 Sheppar and Eberlin, Dec. 4, 1923, for electrodeposition of rubber coatings. Other examples are found in the following copending applications; Serial No. 21,311, filed April 7, 1925, Leon W. Eberlin and Carl L. Beal, for electrode osition of coatings of cellulosic compoun s, and Serial No. 21,341, filed April 7, 1925, Samuel E. Sheppard and Leon W. Eberlin, for electrodcposition of coatings different part, this trouble is especially comprising rubber and a cellulosic compound. Obviously our substrating principle is adapted to the production of coatings of great uniformity wherever electrodeposition takes place from aqueous emulsions or similar dispersions.

lVhen electrodepositing rubber, or cellulosic compound or mixtures thereof in accordance with the patent and applications hereinabove cited, the particles in the emulsions act as if negatively charged, and, therefore, travel toward the anode. Referring to the drawing the electroconducting surface 1 to be plated is covered with a substratum layer 7 as above explained. It is then connected at 2 to anode line 3 to form the anode and is immersed in the emulsion 1. A suitable cathode is also placed in contact with the emulsion. For instance, the latter may be contained in a metal vessel 5 which is connected in the circuit of cathode line 6. The current should preferably be an effectively unidirectional one. It may be a current of constant value, or a direct current of pulsating character. In some instances it is useful to employ an unbalanced alternating current, which is most conveniently obtained by superimposing an alternate current upon a direct current. The voltages and current densities to be employed can vary over a considerable range. Because the voltage of 110 is' conveniently available, We prefer to use it, and regulate the corresponding current density from to (say 4),) of an ampere per square inch of electrode surface to be coated. In gen eral the plating expedients follow the practice given in the patent hereinabove cited.

or convenience we prefer to apply the term substratum herein to coating 7 before, as well as after, the outer coating is electrodeposited upon it,-thus designating it at all times by its ultimate purpose.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. The process of depositing organic material on an electro-conducting surface of an object, which comprises coating said surface with a substratum which forms a diffusion path for the current at said surface, and then bringing said substratumed surface into contact with an electroconducting aqueous emulsion of said organic material and passing a depositing electric current through said surface, substratum and emulsion. 4

2. The process of depositing organic material on an electro-conducting surface of an object, which comprises coating said surface with an organic potentiaLequalizing substratum through which a depositing current can pass, bringing the substratumed surface into contact with an electroconducting aqueous emulsion ofsaid material and passing a depositing electric current through said surface, substratum and emulsion.

3. The process of depositing organic material upon an electroconducting surface of an object, which comprises covering said surface with a hygroscopic coherent substratum Which forms a diffusing path for the electric current at said surface, bringing said substratumed surface into contact with an electroconducting aqueous emulsion of said material and passing a depositing electric current through said surface, substratum and emulsion.

4:. The process of depositing an organic material on an electroconducting surface of an object, which comprises coating said surface with a coherent gelatinous substratum containing a hydroscopic agent, immersing said substratumed surface in an aqueous electroconducting emulsion of said material and passing a depositing electric current through said surface, substratum and emulsion. i

5. The process of depositing rubber on an electroconducting surface of an object, which comprises covering said surface with a substratum forming a. diffusion path for the electric current at said surface, bringing said substratumed surface into contact with an electroconducting aqueous rubber emulsion and passing a depositing electric current through said surface, substratum and emulsion.

6. The process of depositing rubber on an electroconducting surface of an object, which comprises covering said surface with a coherent organic potential-equalizing substratum through which the depositing current can pass, bringing said substratumed surface into contact with an aqueous electroconducting rubber emulsion and passing a depositing electric currentthrough said surface, substratum and emulsion.

7. The process of depositing rubbber on an electroconductingsurface of an object, which comprises covering said surface with a hydroscopic substratum which forms a diffusion path for the electric current at said surface, bringing said substratumed surface into contact with an electroconducting aqueous rubber emulsion and passing a depositing electric current through said surface, substratum and emulsion.

8. The process of depositing rubber on an electroconducting surface of an object,

'which comprises coating said surface with a coherent gelatinous substratum comprising a hygroscopic agent, bringing said substratumed surface into contact with an electroconducting aqueous rubber emulsion and passing a depositing electric current through said surface, substratum and emul- S1011.

9. As a blank in the process of electrodepositing organic material upon a'conducting surface, an object comprising said surface and having on the latter a coherent organic substratum capable of forming a diffusion path for the electric current at the surface and equalizing the electric poten tial thereat.

10. As a blank in the process of electrodepositing organic material on a conducting surface, an object comprising said surface and having on the latter a coherent hygroscopic organic substratum capable of forming a difi'usion path for the electric current and equalizing the potential at said surface.

11. As a blank in the process of electro- 15 depositing rubber on a conducting surface, an object comprising said surface and having on the latter a coherent colloidal substratum containing a hygroscopic agent.

Signed at Rochester, New York, this 14th 20 day of April,- 1925.

SAMUEL E. SHEPPARD. CARL L. BEAL. 

